SD103A-T Schottky Diode Equivalent & Substitute Parts

Part Overview

The SD103A-T is a Schottky rectifier diode manufactured by Diodes Incorporated, rated for 40V DC reverse voltage and 350mA average rectified current in a through-hole DO-35 package. This part is classified as obsolete, necessitating identification of functionally equivalent alternatives for ongoing design support and procurement. Substitute parts must maintain electrical compatibility across voltage, current, and thermal specifications while accommodating different package formats and manufacturer sources.

Key Parameters

Parameter	SD103A-T Value	Unit
Voltage - DC Reverse (Vr) Max	40	V
Current - Average Rectified (Io)	350	mA
Voltage - Forward (Vf) Max @ If	600 mV @ 200 mA	mV @ mA
Reverse Recovery Time (trr)	10	ns
Current - Reverse Leakage @ Vr	5	µA @ 30 V
Capacitance @ Vr, F	50	pF @ 0V, 1MHz
Mounting Type	Through Hole	-
Package / Case	DO-35	-
Operating Temperature - Junction Max	125	°C
Technology	Schottky	-
Speed Classification	Fast Recovery ≤ 500ns, > 200mA	-

Substitute Part Grouping Explanation

Substitution of the SD103A-T is determined by the following critical parameters:

Voltage Rating: Substitute parts must have a DC reverse voltage rating (Vr) equal to or greater than 40V to maintain reverse bias protection.

Current Rating: Substitute parts must have an average rectified current (Io) rating equal to or greater than 350mA to handle the intended load without exceeding thermal limits.

Speed Classification: The SD103A-T exhibits fast recovery characteristics (≤500ns for currents >200mA). Substitute parts with equivalent or superior speed performance maintain switching efficiency.

Forward Voltage: Forward voltage drop at rated current affects power dissipation. The SD103A-T specifies 600mV @ 200mA; substitutes with comparable or lower forward voltage reduce thermal stress.

Package Compatibility: The through-hole DO-35 package is the primary form factor. Surface-mount alternatives (SOD-123) require circuit board redesign but offer electrical equivalence.

Reverse Leakage: Leakage current at rated reverse voltage affects standby power consumption and circuit performance. The SD103A-T specifies 5µA @ 30V.

Substitutes are grouped into two categories: Direct Electrical Equivalents (matching or exceeding all critical parameters) and Functional Alternatives (meeting voltage and current requirements with acceptable trade-offs in secondary parameters).

Parameter Comparison

Part Number	Manufacturer	Vr (Max) V	Io (mA)	Vf (Max) @ If	trr (ns)	Ir @ Vr	Package	Mount Type	Status
SD103A-T	Diodes Inc.	40	350	600 mV @ 200 mA	10	5 µA @ 30 V	DO-35	Through Hole	Obsolete
SD103AW-7-F	Diodes Inc.	40	350	600 mV @ 200 mA	10	5 µA @ 30 V	SOD-123	Surface Mount	Active
BAT48	STMicroelectronics	40	350	750 mV @ 200 mA	Fast Recovery ≤ 500ns	25 µA @ 40 V	DO-35	Through Hole	Active
1N5825	Microchip Technology	40	5000	380 mV @ 5 A	Fast Recovery ≤ 500ns	10 mA @ 40 V	TOP HAT	Through Hole	Active
1N6677-1	Microchip Technology	40	200	500 mV @ 200 mA	Small Signal ≤ 200mA	5 µA @ 40 V	DO-35	Through Hole	Active
BAT42	STMicroelectronics	30	200	1 V @ 200 mA	5 ns	500 nA @ 25 V	DO-35	Through Hole	Active
1N5712-1	Microchip Technology	20	75	1 V @ 35 mA	Small Signal ≤ 200mA	150 nA @ 16 V	DO-35	Through Hole	Active
1N6857-1	Microchip Technology	20	150	750 mV @ 35 mA	Small Signal ≤ 200mA	150 nA @ 16 V	DO-35	Through Hole	Active
DSB0.2A20	Microchip Technology	20	200	500 mV @ 200 mA	Small Signal ≤ 200mA	5 µA @ 20 V	DO-35	Through Hole	Active
DSB0.5A20	Microchip Technology	20	500	650 mV @ 500 mA	Fast Recovery ≤ 500ns	10 µA @ 20 V	DO-35	Through Hole	Active

Engineering Selection Recommendations

Primary Substitute: BAT48 (STMicroelectronics)

The BAT48 is the closest functional equivalent to the SD103A-T. It maintains identical voltage (40V) and current (350mA) ratings in the same through-hole DO-35 package. Forward voltage is 750mV @ 200mA compared to 600mV for the SD103A-T, representing a 150mV increase in forward drop. Reverse leakage is 25µA @ 40V versus 5µA @ 30V for the original part. The BAT48 is ROHS3 compliant and carries active product status. This part is suitable for direct replacement in existing through-hole designs without circuit board modification.

Secondary Substitute: SD103AW-7-F (Diodes Incorporated)

The SD103AW-7-F is electrically identical to the SD103A-T, offering the same voltage, current, forward voltage, and reverse recovery characteristics. It is manufactured by the same supplier as the original part and carries active product status with ROHS3 compliance. The primary difference is the SOD-123 surface-mount package, which requires circuit board redesign. This option is preferred for new designs or board revisions where surface-mount technology is acceptable.

Voltage-Rated Alternatives

Parts with 40V ratings but different current capabilities serve specific applications:

The 1N5825 (Microchip Technology) provides 40V rating with significantly higher current capacity (5A) in a TOP HAT through-hole package. This part is suitable for applications requiring higher current handling than the 350mA specification of the SD103A-T.

The 1N6677-1 (Microchip Technology) provides 40V rating with 200mA current capacity in DO-35 package. This part is suitable for applications with lower current requirements than the SD103A-T.

Lower Voltage Alternatives

Parts with voltage ratings below 40V are not recommended as direct substitutes for the SD103A-T. The BAT42 (30V), 1N5712-1 (20V), 1N6857-1 (20V), DSB0.2A20 (20V), and DSB0.5A20 (20V) do not meet the 40V reverse voltage requirement and introduce risk of reverse bias failure in circuits designed for 40V operation.

Compliance Considerations

The SD103A-T is ROHS3 compliant. The BAT48 and SD103AW-7-F maintain ROHS3 compliance. Several Microchip alternatives (1N5712-1, 1N6677-1, 1N6857-1, DSB0.2A20, DSB0.5A20) are RoHS non-compliant and should be evaluated against procurement and regulatory requirements.

Frequently Asked Questions (FAQ)

Q: Can the BAT48 replace the SD103A-T in all applications?

A: The BAT48 meets the critical voltage (40V) and current (350mA) specifications and uses the same through-hole DO-35 package. The forward voltage is 150mV higher (750mV vs. 600mV @ 200mA), which increases power dissipation by approximately 30mW at rated current. Thermal design must accommodate this increase. Reverse leakage is 25µA @ 40V compared to 5µA @ 30V for the SD103A-T. Applications sensitive to leakage current should be evaluated. The BAT48 is suitable for most general-purpose rectification applications.

Q: Why is the SD103AW-7-F not a direct replacement despite identical electrical specifications?

A: The SD103AW-7-F is electrically identical to the SD103A-T but uses the SOD-123 surface-mount package instead of the through-hole DO-35 package. Existing circuit boards designed for through-hole components cannot accommodate surface-mount packages without physical redesign. The SD103AW-7-F is the preferred choice for new designs or board revisions where surface-mount technology is implemented.

Q: Can lower voltage-rated parts (20V or 30V) be used in place of the SD103A-T?

A: No. The SD103A-T is rated for 40V reverse voltage. Substituting parts with lower voltage ratings (BAT42 at 30V, 1N5712-1 at 20V, etc.) introduces risk of reverse bias breakdown if the circuit operates at or near 40V. These parts are not suitable for direct replacement.

Q: What is the significance of the "Fast Recovery" speed classification?

A: The SD103A-T exhibits fast recovery characteristics (≤500ns for currents >200mA), which reduces switching losses in high-frequency applications. The BAT48 also provides fast recovery performance. Parts classified as "Small Signal" (1N5712-1, 1N6677-1, 1N6857-1, DSB0.2A20) have slower recovery times and are suitable for lower-frequency applications. Selection depends on circuit switching frequency requirements.

Q: How does forward voltage affect circuit performance?

A: Forward voltage drop directly affects power dissipation in the diode. The SD103A-T specifies 600mV @ 200mA. The BAT48 specifies 750mV @ 200mA, representing a 25% increase in forward drop. In rectification circuits, higher forward voltage reduces output voltage and increases heat generation. The 1N6677-1 specifies 500mV @ 200mA, which is lower than the SD103A-T and reduces power dissipation. Circuit design must account for these differences in voltage regulation and thermal management.

Q: What is the impact of reverse leakage current on circuit design?

A: Reverse leakage current flows when the diode is reverse-biased. The SD103A-T specifies 5µA @ 30V. The BAT48 specifies 25µA @ 40V, representing a 5-fold increase. In high-impedance circuits or precision analog applications, elevated leakage current may degrade performance. The 1N6677-1 specifies 5µA @ 40V, matching the SD103A-T leakage characteristic. Applications requiring low leakage should prioritize parts with comparable or lower leakage specifications.

Q: Are there compliance differences between substitute options?

A: The SD103A-T and BAT48 are both ROHS3 compliant. The SD103AW-7-F is also ROHS3 compliant. Several Microchip alternatives (1N5712-1, 1N6677-1, 1N6857-1, DSB0.2A20, DSB0.5A20) are RoHS non-compliant. Procurement specifications and regulatory requirements must be evaluated to determine acceptable alternatives. The 1N5825 is ROHS3 compliant.

Q: What package options are available for the SD103A-T?

A: The SD103A-T uses the through-hole DO-35 package. The SD103AW-7-F provides the same electrical specifications in the surface-mount SOD-123 package. The 1N5825 uses a TOP HAT through-hole package with higher current capacity. All other listed alternatives use the through-hole DO-35 package. Package selection depends on circuit board design and manufacturing capabilities.

Q: How should I evaluate a substitute part for a specific application?

A: Verify that the substitute part meets or exceeds the following minimum requirements: (1) DC reverse voltage rating ≥ 40V, (2) average rectified current rating ≥ 350mA, (3) operating temperature range compatible with circuit requirements, (4) forward voltage and reverse leakage acceptable for circuit performance, (5) package format compatible with circuit board design, and (6) compliance certifications (ROHS, REACH) aligned with procurement requirements. Thermal analysis should account for differences in forward voltage and leakage current between the original part and substitute.

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